# AIKeyboard — HeliBoard + Gemma 4 On-Device AI Correction

HeliBoard fork that adds on-device spell and grammar correction powered by
**Gemma 4 E2B-it** running locally via Google's **LiteRT-LM** SDK.

After you finish typing a sentence (`.`, `!`, `?`), the model silently checks
it and — if it finds an error — shows the corrected sentence in the suggestion
strip. Tap it once to replace the original text. Everything runs on-device,
no network, no cloud API.

---

## How it works

```
User types "guten rag."
          ↓
InputLogic detects sentence-ending punctuation
          ↓
AiTriggerHook (500 ms debounce) extracts last sentence
          ↓
AiCorrectionEngine.correctSentence()
  → LiteRT-LM Engine (GPU first, CPU fallback)
  → Gemma 4 E2B-it .litertlm model
          ↓
AiSuggestionManager.postSuggestion("Guten Tag.", "guten rag.")
          ↓
Suggestion strip shows "Guten Tag." in italic/accent color
          ↓
User taps → original text replaced with correction
```

### Components

| File | Role |
|------|------|
| `app/…/ai/AiCorrectionEngine.kt` | LiteRT-LM wrapper; GPU→CPU fallback |
| `app/…/ai/AiTriggerHook.kt` | Sentence detection + debounce |
| `app/…/ai/AiSuggestionManager.kt` | Posts corrected text to suggestion strip |
| `patches/0001-InputLogic-ai-hook.patch` | Hook in `InputLogic.java` after `commitCodePoint` |
| `patches/0002-LatinIME-ai-lifecycle.patch` | AI object lifecycle in `LatinIME.java` |
| `patches/0003-SuggestionStrip-ai-style.patch` | Italic + accent color for AI suggestions |

---

## Requirements

- Android device with **ARM64** (arm64-v8a), Android 11+ (API 31)
- Android Studio **Ladybug** or newer / Gradle 8+
- NDK **28.0.13004108**
- **Gemma 4 E2B-it** model in `.litertlm` format (~2.6 GB)  
  Download: <https://huggingface.co/litert-community/gemma-4-E2B-it-litert-lm>

---

## Setup

### 1. Clone and prepare HeliBoard sources

```bash
git clone http://172.17.2.68:3001/nova/AIKeyboard.git
cd AIKeyboard
bash setup_heliboard.sh
```

`setup_heliboard.sh` clones HeliBoard from GitHub and applies the three AI
integration patches automatically.

### 2. Push the model to the device

```bash
adb push gemma-4-E2B-it.litertlm /data/local/tmp/gemma-4-E2B-it.litertlm
adb shell chmod 644 /data/local/tmp/gemma-4-E2B-it.litertlm
```

### 3. Build and install

```bash
./gradlew installDebug
```

Enable **AIKeyboard** as your input method in Android Settings → System →
Languages & input → On-screen keyboard.

---

## Patch details

The three patches modify HeliBoard source files in `heliboard/`:

**0001 — InputLogic hook**  
After every committed code point, checks `AiTriggerHook.isSentenceEnder()`.
On a sentence-ender, reads up to 500 chars before the cursor and calls
`onSentenceEndDetected()`.

**0002 — LatinIME lifecycle**  
Instantiates `AiCorrectionEngine`, `AiSuggestionManager`, and `AiTriggerHook`
in `onCreate()`, cleans them up in `onDestroy()`. Overrides
`showAiSuggestion()` to bypass the normal suggestions-enabled gate and
intercepts `pickSuggestionManually()` to do a clean sentence replacement
(finish composing → delete original → commit corrected text).

**0003 — SuggestionStrip styling**  
Detects the `KIND_AI_FLAG` bit (`0x10000`) on a `SuggestedWordInfo` and
applies italic style + auto-correct accent color to visually distinguish AI
suggestions from normal word predictions.

---

## Model placement

The model must be at `/data/local/tmp/gemma-4-E2B-it.litertlm` on the device.
This path is configured in `AiCorrectionEngine.MODEL_PATH`.

The model file is **not** tracked in this repository (2.6 GB, `.litertlm` is
in `.gitignore`).

---

## Backend selection

`AiCorrectionEngine` tries **GPU** (WebGPU/Vulkan via LiteRT-LM) first.
If GPU initialization fails, it falls back to **CPU** immediately. If a GPU
inference error occurs at runtime, it permanently switches to CPU for the
session and recreates the engine.

Tested on:
- Google Pixel 7 (Tensor G2) — CPU backend (OpenCL not available)
- Devices with Mali-G710 — GPU via WebGPU/Vulkan

---

## License

The AI integration layer (`app/src/main/java/helium314/keyboard/latin/ai/`)
is original work added to this project.

HeliBoard itself is licensed under **GPL-3.0-only**. See
`heliboard/LICENSE` after running `setup_heliboard.sh`.